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if you do what do you think ?
LT
Edits: 05/11/16Follow Ups:
Pete
I use them for GS but use the Koa Speer because they are identical to the Kwammies and a fraction of the cost..Koa made the Kwammies. The SPR series.You should be using CC as GS tho like Jim and Eli suggests.
A friend you get for nothing,an enemy has to be bought
Edits: 05/12/16
Not even re-labeled or hardly even re-branded.
Re-packaged?
HI Mike.
the Koa resistors is metal film . I have a lot of new old stock CC but they drip quite badly .
KOA made CC, but mouser and others have phased out selling them. There may be some left in 820 Ohm or the like remaining, perhaps at Mouser or Digikey. The 1KOhm weren't available the last time I looked.Edit: Just checked Mouser, Digikey and Allied (US sources). There is nothing showing. Where have others seen KOA Speer CC resistors?
Edits: 05/12/16 05/12/16
No shortage of KOA Speer Carbon Film "Killwammy" resistors
Heh, yes, the carbon film ones are indeed there. Did you find any carbon comps? I couldn't find them, and that's what I had meant when I posted about for grid stoppers. I also use the CFs for other locations.
Ohmite works fine in most cases for Carbon Comps.
--Jeff
Jeff,
As the uploaded graphic shows, Mouser carries carbon comp. resistors by several makers. Xicon brand are fine and probably the best value.
Eli D.
Some manufacturers are now producing "carbon composition" resistors that are in fact spiral wound. I first encountered this when replacing the parasitic suppressors in a HF transmitter about 20 years ago. The new resistors didn't work, and I had to scrape the outer layer off one to understand why. So, a word to the wise - any carbon comp types purchased new from a general supply house like Mouser or Digikey should be inspected for this before you use them.
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Buy Chinese. Bury freedom.
Yes, I use them. They add little if any noise and do their job well.
I have not used Kiwame in that position, but i have tried all the other types except wire wound. It seems that i prefer metal film for its clean neutral quality over the other types. Although i have some vintage non inductive wire wounds that i have not tried yet. I have used the Kiwame as plate load and on the cathode where they perform well. cheers,
I use Mills Non-inductive wirewounds.
I find that grid stoppers optimal Ohmic values are audible to a FRACTION of an Ohm, and one can carefully, meticulously, "bracket" and find the precise value.
That is a different question that what you asked. In my earliest building years, I found this to be true.
In the SET 45 DC amps I do now, I use no grid stoppers at all. Less is more .....sometimes !!
Jeff Medwin
I try to use carbon comps and not carbon film. I can't remember why comps are better than film.I've been using Riken 1/2-watt and 1-watt resistors. Have a stash of them.
As you know, dressing and soldering of these resistors onto sockets are as important as what type of resistor is used. As little lead, from resistor body to socket tang.
Edits: 05/11/16
what i concern about the use of carbon comps is noise , carbon film seem to be better in this regard .
what value riken 1/2 watt you got ?
LT
Since the current through the grid stopper is miniscule the "microarcing" noise from a carbon comp resistor is not an issue. I try to use them whenever possible. The near total lack of inductance makes them the right part.
thanks Jim.
i also think how much resistance to use is importance as well .
i always use as small value as i think it get the job done , however i seen some people use up to 10k on grids stopper and i think this is way too much .
Yes, carbon composition is the "correct" construction for grid stoppers, as that type of resistive material is both non-metallic and non-inductive. Hold the amount of metal attached to the socket lug to a minimum. An antenna for parasitic oscillation is very bad here.
The value used for grid stoppers depends greatly on the gm of the type being employed. High gm types are much more vulnerable to parasitic oscillation. A 100 Ω part is fine for the 12AX7 triode. OTOH, a minimum of 10 KOhms should be used at each of the 4 grid connections of a 5842.
Eli D.
"a minimum of 10 KOhms should be used at each of the 4 grid connections of a 5842."
That's really interesting. Because all the grids are connected internally, I have only put stoppers on the signal input. I have seen photos of a little pyramid of grid resistors connected to the input signal, but have never tried it.
"I have seen photos of a little pyramid of grid resistors connected to the input signal, but have never tried it."
That's exactly the way to do things. The 5842 and its Russian counterpart, the 6C45П (6s45p), come annoyingly close to oscillating inside the cardboard box. :> ( The slightest bit of stimulus will trigger those VERY high gm types, which were designed for grounded grid RF service, into oscillation, when they are set up common cathode. Even a 200 MHz. o'scope might not catch where those buggers can oscillate. Take no prisoners! CC stoppers on all grid connections, a carbon stopper of some kind on the plate, and ferrite beads on the heater wires are very much in order, when "in box oscillators" are to be employed.
Eli D.
"Even a 200 MHz. o'scope might not catch where those buggers can oscillate. "
That's what scares me! My 60 MHz Tektronix would be blissfully ignorant. Thanks, Eli.
And that tube's parameters (voltage and current). If instance, most Fender amps use 1.5K-ohm resistors on their 6L6GC amps. Marshall uses 5.6K-ohm resistors on their EL34 amps.
Noise only occurs where there is current. There is virtually no current driving a grid.
One of the problems using a spiral-wound component in this application is the difficulty in testing for spurious responses (oscillations). Such responses may occur only when signal is present, and may appear only for brief intervals as the signal crosses the zero point, or on positive or negative peaks. The only definitive tool for this is a spectrum analyzer with a bandwidth of several hundred MHz. Lacking this instrument, the only resistor safe for a DIYer to use in either the grid or anode is carbon comp. Failing to hear anything amiss after installing something else is no guarantee that the amplifier isn't oscillating.
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Buy Chinese. Bury freedom.
Variety of values. I have primarily 1800-ohm, 1-watt used to replace grid stoppers in most Fender amp that use 1500-ohms. Can't seem to find any 1/2-watt resistors close to 1500-ohm value.
I like them too for grid stops, but where can you get them these days, if anywhere?
I got some from Parts Connexion, about a year ago.
Carbon films are spiral wound. NG for grid stoppers.
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Buy Chinese. Bury freedom.
nt
nada aqui
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Buy Chinese. Bury freedom.
I agree that for a grid stopper, carbon is the classic choice for lack of inductance, but I have often wondered whether a tiny bit of inductance would be so bad, so long as the resistor does not reach a frequency where it then becomes capacitative. If it's purely and only slightly inductive, wouldn't that work OK? The increase in impedance with rising frequency is compatible with the rationale behind using a grid-stopper in the first place. Or so I think.
I did not realize that carbon film resistors could be inductive; thanks for pointing that out.
"The increase in impedance with rising frequency is compatible with the rationale behind using a grid-stopper in the first place."
In many tubes the grid will oscillate with nothing connected to it at all. It must be anchored or dampened with a lo-Z connection to prevent that. Inserting an inductor allows the grid to "wiggle" as the frequency increases and will promote oscillation.
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Buy Chinese. Bury freedom.
Wouldn't the resistive component of a helical resistance element entirely swamp the inductive component above 100 ohms or so?
"Wouldn't the resistive component of a helical resistance element entirely swamp the inductive component"
A more important question is whether it will swamp the oscillation. Some tubes will oscillate even when the grid is grounded. The 811A is an example of this. Other tubes have a grid structure whose internal inductance needs only the tiniest amount of additional, external inductance to set them off. In the context of your question, each amplifier would need to be approached on a case by case basis if the goal is indeed to determine what the designer can "get away with." I don't have time for that, so I use carbon comp. It's not clear to me why anyone would use anything else for this purpose. There's no downside.
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Buy Chinese. Bury freedom.
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